1. Field of the Invention
The present invention relates to a semiconductor memory device, for example, a NAND type flash memory.
2. Description of the Related Art
The NAND type flash memory has two kinds of programming or reading systems. First, there is an Even/Odd system (hereinafter, referred to as an E/O system) in which even cells and odd cells of plural cells connected to a selected word line are selected alternately and the halves of the plural cells are connected to corresponding bit lines alternately. Secondly, there is an All Bit Line system (hereinafter, referred to as an ABL system) in which all plural cells connected to a selected word line are connected to corresponding bit lines and data are collectively programmed or read.
In the E/O system, since the cells connected to the odd and even bit lines cannot be programmed simultaneously, a pair programming operation cannot be carried out. For this reason, there is a problem that probability that a threshold value is changed by coupling with adjoining cells is increased.
In the ABL system, although both operations of the pair programming and an even/odd programming can be carried out, a chip area is expanded and also a consumed current is increased because it is necessary to connect a sense amplifier to each bit line.
Incidentally, as a related art, there is an art that a bit line connected to a sense amplifier 1 and a bit line connected to a sense amplifier 2 are disposed alternately, and thereby noise due to capacitive coupling between the bit lines is reduced.